Lecture 13Plate TectonicsContinental drift TheoryIntroduced by Alfred L. Wegener in his book “The Origin of Continents and Oceans” in 1915Pangea – the supercontinent which broke up during the late Permian = Gondwanaland + LaurasiaEvidence for continental drift1.Jigsaw puzzle fit2.Fossils(e.g.Lystrosaurus, Cygnognathus,Mesosaurus, Glossopteris)3.Rock type and structural similarities-rocks found in one continent closely match (in age and type) those rocks found in the matching continent-matching mountain belts4.Paleoclimatic evidence -layers of glacial deposits (same age) found in S. Africa and S. America, India and Australia-coal forms under tropical climatesSea Floor Spreading Hypothesis-introduced by Harry Hess in the early 1960s- New material is being formed along mid-oceanic ridges- Wilson CycleDevelopment of the theory- Extensive mapping of ocean floor ðyoung age of ocean floor (130 m.y.)- Oldest rocks from continents ðbillions of years oldPaleomagnetismEarth’s magnetic field:Declination

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